Depends on your definition of max level. Technically i think winterapring has the highest average mob level.
Id consider anything 50+ to be max level. That gives us ungoro, silithus, both plague lands, wintersprings, burning steeps. Something like that.
Kalimdor. All of kalimdor. Enough said.
Where ever the bread crumbs take me, my friend.
Is Carbonite a quest tracker? I am 100% not going to do that.
I will play human, so I will go:
Elwynn
Westfall (miss old non Horatio Westfall)
Redridge
Duskwood
Alterac/Desolace
Tanaris/Hinterlands
Searing Gorge
Blasted Lands
WPL
EPL
Throw in a few random zones in between when I want to explore, change of scenery, like Desolace and Winterspring.